Accurate surface-to-bulk feature alignment and feature size preservation during double-sided wafer processing using C4F8 plasma polymer for the fabrication of electrostatically actuated cantilever devices

An accurate alignment of surface-to-bulk features (within ±;2μm) during a double-sided silicon wafer processing can be extremely difficult. This is due to a combination of mask misalignment errors and unreliability of bulk etching techniques in translating the bulk feature shapes down to the surface side. In this paper, we present a fabrication process for an electrostatically actuated cantilever device where an accurate surface-to-bulk feature alignment is imperative to the operation of the device. The fabrication process compensates for the bulk etch-induced feature size variation and mask misalignment errors using a combination of self-aligning features and C ₄F₈ plasma polymer passivation.